Semi-conductive device and method for making same



F. WEIL July 22, 1958 SEMI-CONDUCTIVE DEVICE AND METHOD FOR MAKING SAME Filed July 21, 1955 INVENTOR FRITS WEIL United States Patent O SEMI-CGNDUCTIVE DEVICE AND METHOD FOR MAKING SAME Frits Well, Eindhoven, Netherlands, assignor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application July 21, 1955, Serial No. 523,403

Claims priority, application Netherlands July 23, 1954 '7 Claims. (Cl. 317-235) This invention relates to semi-conductive devices, and in particular to transistors and crystal diodes, and to methods of making the same.

It is known to enclose semi-conductive devices in an envelope and to seal a plurality of current supply or leadin wires in this envelope. The envelope is usually made of glass; however, it may be made of ceramic material or of ceramic material and glass. Part of the envelope may even be made of metal. It is also known that the semi-conductive materials employed, more particularly, germanium and selenium, and to a smaller extent also silicon, are sensitive to heat, so that care must be taken to prevent excessive heating of the semi-conductive body when the conductors or lead-in wires are sealed in the envelope.

On the other hand, it is desirable that the heat developed by the passage of current in the semi-conductive body during operation of the device is satisfactorily dissipated.

It is difiicult to meet these two requirements at the same time: for the sealing-in operation, it is necessary to provide long and thin supply conductors, so that they transfer only a small amount of heat developed during the formation of the seal to the semi-conductive body; during operation of the device, on the other hand, it is advantageous to have short and thick, i. e., massive, conductors, so that they can satisfactorily transfer the heat developed in the body.

The chief object of the invention is to provide a semiconductive device fulfilling both of the above requirements, and to furnish a method for manufacturing such devices.

In accordance with the invention, after the supply conductors have been sealed into the envelope, at least one supply wire is provided over at least part of its length adjacent the envelope with a metal coating. This is carried out at a temperature which does not affect the semiconductive body. The coating may be applied in a very simple manner by electroplating. However, as an alternative, the coating may be applied by Schoops method, which involves spraying of molten metal in finely divided particles. As a further alternative, the coating may be constituted by a metal wire or a metal tape winding. The additional mass afforded by this external coating improves the heat-dissipating ability of the supply wire covered.

The invention Will now be described with reference to the accompanying drawing, wherein:

Figs. 1, 2 and 3 show, on an enlarged scale, several different embodiments of the invention employed in connection with transistors.

Referring to the drawing, the transistors shown therein are provided with glass envelopes, which are constituted by a unilaterally closed glass tube 1 having a sealed-onp 2,844,772 Patented July 22, 1958 z glass lid or header 2. In each lid is sealed a plurality of current supply or lead-in wires 3, which extend therethrough and are connected to an electrode system inside the envelope, this system being connected with a semiconductive body 4 in the conventional manner. The supply wires 3 are comparatively thin in order that the heat applied during the sealing of the glass lid 2 does not produce more than a permissible, predetermined increase in temperature of the heat-sensitive, semi-conductive body 4.

The invention resides in that, after the envelope has been sealed, one or more of the wires projecting from the envelope is provided with a metal coating or layer. In the transistor shown in Fig. 1, this coating or layer of metal is applied to all wires by an electroplating op eration. It is preferably constituted by a copper layer 5. Thus the diameter of the external, coated wire 5 is greater than that of the internal, uncoated wire 3.

With the transistor shown in Fig. 2, the part of the wires3 adjacent the envelope is provided with a sprayed layer of aluminum 6. The ends of the wires are left uncoated, so that it is not difficult to carry out a soldering connection with these ends.

With the tra-nistor shown in Fig. 3, the supply Wire 3 leading to one electrode has wound on it a layer of copper wire 7. It is assumed that the largest quantity of heat is developed in this electrode. This wire 7 may then be soldered to the supply wire 3, so that the thermal contact is improved. The increase in temperature during the soldering operation is low compared to that occurring during the sealing-in operation.

It should be noted that the figures are only diagrammatical views; in particular, the length of the supply wires inside the envelope is shown on an enlarged scale for the sake of clarity.

While I have described my invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.-

What is claimed is:

1. A method of housing a heat-sensitive, semi-conductive device having thin, connecting wires secured thereto, comprising enclosing said device within an envelope and sealing the connecting wires into said envelope by the application of heat, said thin wires preventing the heat of the sealing operation from being transferred to and damaging the semi-conductive device, and thereafter providing a portion of a connecting wire adjacent and external to the envelope with a metal layer of sufiicient mass at which the resultant wire and layer provide a significant improvement in heat dissipation of the device when energized.

2. A method as claimed in claim 1 in which the layer is provided by electroplating the said wire portion.

3. A method as claimed in claim 1 in which the layer is provided by spraying molten metal onto the said wire portion.

4. A method as claimed in claim 1 in which the layer is provided by winding a metal member around the wire.

5. In a heat-sensitive, semi-conductive device comprising an envelope with thin, lead-in wires sealed in said envelope, the improvement comprising a metal layer provided on a lead-in wire external to the envelope but adjacent thereto, the combined wire and layer having a diameter exceeding that of the portion of the wire inside i said wire.

3 4 the envelope and possessing sufiicient mass to provide 21 References Cited in the file of this patent fiilfiigznigiime zirovement in heat dissipation of the device UNITED STATES PATENTS 6. A Semi-conductive device as claimed in claim 5 in 1,540,137 q h g r June82, 1925 which the layer comprises a plated layer f metal, 5 2,392,661 Gremqr an- 1946 A ctive device as claimed in claim 5 in 24 23 2 ig g Gav-111, 3g wh' h th 1 6 y pn a metal member wound about 2,745,045 Ingraham y 1956 

